The present invention relates generally to apparatus for introducing a process gas into a treatment chamber and, more particularly, to an apparatus for introducing a process gas into a liquid-gas contact zone surrounding a liquid spray apparatus disposed to spray a liquid into the treatment chamber.
There are many applications in the art wherein a process gas must be introduced into a treatment chamber to contact a liquid within the chamber. For example, in the drying of foodstuff, such as milk or slurries of food products, it is common to spray the liquid into a spray dryer where the liquid is contacted with hot air to dry the milk or foodstuff to produce a powder. Such spray dryers are also utilized for the absorption of pollutants from hot flue gases by spraying a slurry of particulate absorbent into a drying chamber and contacting the particulate slurry therein with hot flue gas whereby the particulate absorbent reacts with pollutants in the flue gas to remove the pollutants therefrom as a dry salt.
In such apparatus, the liquid, which may be a homogeneous solution or slurry of suspended particulate material, is atomized by means of a spray apparatus, such as a nozzle or an atomizer wheel, arranged centrally in a treatment chamber defined by a treatment vessel. The atomized spray is directed radially outward from the liquid spray apparatus into a liquid-gas contact zone in the form of an umbrella-like spray cloud. The process gas is introduced annularly about the liquid spray apparatus into the liquid-gas contact zone as uniformly as possible to contact the atomized liquid passing radially outward from the spray apparatus. Typically, the process gas is passed through a supply duct into one or more conical ducts disposed concentrically about the liquid spray apparatus and opening into the treatment chamber. As the process gas passes through the gas supply duct, a rotational motion may be imparted to the gas so that it enters the treatment chamber through the conical inlet ducts in a swirling fashion. The conical inlet ducts are designed to guide the process gas into the liquid-gas contact zone surrounding the liquid spray apparatus. Examples of this type of gas distribution device may be found in U.S. Pat. Nos. 3,803,723, 4,226,603, 4,227,896, and 4,481,171.
In some applications, particularly when utilized as flue gas scrubbing devices, spray dryers must operate over a wide range of gas flow volumes. Thus, it is desirable to provide a gas flow distribution apparatus which is capable of supplying process gas to the liquid-gas contact zone over a wide range of gas flow volume at a relatively constant velocity to insure proper mixing of the atomized particulate absorbent slurry with the process gas in the liquid-gas contact zone. Accordingly, it is an object of the present invention to provide an apparatus for introducing a process gas into a treatment chamber wherein a velocity can be maintained above a minimum acceptable level in the region surrounding the liquid spray apparatus so as to insure proper mixing of the atomized liquid with the process gas being introduced into the treatment chamber over a wide range of turndown.